Preparation and evaluation of a novel wound dressing sheet comprised of β-glucan–chitosan complex

A transparent wound dressing sheet was obtained by forming a complex between β-glucan and chitosan (CS). These materials were chosen for their biocompatible, bioabsorbable, and biodegradable properties, and they were expected to promote the therapeutic efficacy of the dressing by increasing the wound healing response. The therapeutic efficacy of the β-glucan–CS complex sheet as a wound dressing was evaluated in wounds created on the dorsal surfaces of mice. β-glucan–CS complex sheets demonstrated therapeutic efficacies comparable or superior to that of Beschitin®W, a commercial wound dressing made from CS. Additionally, the β-glucan–CS complex sheet did not dissolve during the application period, did not adhere to wounds, and was easy to remove. Cumulatively, these results indicate that β-glucan–CS complex sheets are a promising new wound dressing product.     

Reactive grid-assisted co-sputtering of titanium and chromium in a pure nitrogen atmosphere: Uniformity,optics, and structure of the Ti–Cr–N films

This study provides the results of the first attempt to deposit thin films by reactive grid-assisted co-sputtering with the deployment of small grounded grids having two varying apertures for enabling the transfer of particles. The diameter of all the grids utilized was 50 mm, and their apertures' diameters were changed from 5 mm to 15 mm. Furthermore, the ratios of the grid area to the chamber wall area were lower than 0.0161, preventing the formation of ion-rich sheaths and their adverse impact upon discharge and plasma stability. Accordingly, Ti₁Cr_1-xN films (0.88 < x < 0.97) with low chromium contents were deposited on soda-lime glass substrates by using pure nitrogen as the sputtering gas. The grazing incidence X-ray diffraction patterns of the films, the average thicknesses of which were lower than 50 nm, showed no sign of crystallinity in the films. Ranging from 3.26 to 3.79 eV, the optical bandgap of the films changed by altering the apertures’ size; chromium content, internal stress, and quantum confinement effect appeared to be the main contributing factors. The photoluminescence intensities appertaining to trap state emissions reflected a decreasing trend by increasing the chromium content, which can be ascribed to the capability of the chromium particles included in the surface, structure, and grain boundaries of the films to prevent photoinduced electron-hole pairs from recombination. It was found that not only is the grid-assisted co-sputtering method an effective tool whereby the doping range of conventional co-sputtering methods can be significantly extended but also it can cover a spectrum of surface morphologies. However, in comparison with the conventional co-sputtering method, the utilization of the grids with fairly small apertures can limit the thickness uniformity of the films; this effect may be attenuated by changing the geometry and design of grids.     

Cyclo-depolymerizations of polycarbonates in solution: Use of the macrocyclic oligomers obtained in entropically-driven ring-opening polymerizations and copolymerizations to give carbonate–carbonate and carbonate–carboxylate ester copolymers

We report cyclo-depolymerizations of solutions of poly(bisphenol-A carbonate) and two poly(alkylene carbonate)s to give, in each case, mixtures of macrocyclic oligomers (MCOs). The aromatic carbonate was less reactive than the aliphatic carbonates. Using various catalysts small-scale entropically-driven ring-opening polymerizations (ED-ROPs) of the MCOs reformed the original polymers. Tetra-n-butylammonium tetraphenylborate was the most generally useful catalyst of those investigated. At 230 °C in the absence of added catalyst the aliphatic carbonate-containing MCOs underwent thermal ED-ROPs. In order to probe the possibility of extending the use of ED-ROP for copolymer synthesis, copolymerizations of the carbonate-containing MCOs, both with each other and with carboxylate ester-containing MCOs were investigated. These afforded a range of copolymers in high yields, several of which were shown by ¹³C NMR spectroscopy to have the repeat units in random sequences. This approach to the synthesis of copolymers containing carbonate linkages has the potential to be used for the synthesis of polymer libraries.     

Investigation of catalytic activity of cobalt–Schiff base complex covalently linked to the polyoxometalate in the alkene and benzyl halide oxidation with hydrogen peroxide

The catalytic activity of a hybrid compound Co(salen)–POM (1) consisting of cobalt(salen) [salen = N,N′-bis(salicylidene)ethylenediamine] complex covalently linked to a Keggin type polyoxometalate (POM) was studied, for the first time, in the oxidation of various olefins in acetonitrile, using hydrogen peroxide as an oxygen source. The complex (1) can catalyze oxidation of various olefins including non-activated terminal olefins. The effect of other parameters such as solvent, oxidant and temperature were also investigated. The selective oxidation of benzyl halides to their corresponding carbonyl compounds by complex (1), as catalyst, was also examined at room temperature.     

Synthesis and characterisation of highly dispersed Ni/SiO2 catalysts prepared by gas-phase impregnation/decomposition (GPI/D) of a Ni(II) β-diketonate precursor complex

Silica-supported nickel catalysts have been prepared by a solventless technique involving the deposition of the [Ni(tmen)(acac)₂] precursor from the gas phase. According to UV–vis and IR spectroscopy and to elemental analysis, the initial deposition step results in the grafting of Ni(II) complexes on silanol groups to give predominantly [Ni(acac)₂ (Si-OH)₂]⁰ monomeric inner-sphere complexes, with elimination of the neutral (tmen) ligands into the gas phase. Subsequent thermal treatments in oxidising atmospheres causes an oxidative decomposition of the (acac) ligands without nickel desorption or coalescence into oxide crystallites. The ensuing coordinatively unsaturated Ni(II) centres are reduced to Ni(0) by flowing hydrogen at low temperatures (300 °C), yielding nanosized Ni particles as evidenced by TEM and O₂ titration. Thus, the gas-phase deposition technique represents an interesting alternative to conventional wet deposition procedures since it allows one to obtain well-dispersed supported nickel catalysts by reduction at low-temperatures.     

21-Component compositionally complex ceramics: Discovery of ultrahigh-entropy weberite and fergusonite phases and a pyrochlore–weberite transition

Two new high-entropy ceramics(HECs)in the weberite and fergusonite structures,along with the unexpected formation of ordered pyrochlore phases with ultrahigh-entropy compositions and an abrupt pyrochlore–weberite transition,are discovered in a 21-component oxide system.While the Gibbs phase rule allows 21 equilibrium phases,9 out of the 13 compositions examined possess single HEC phases(with ultrahigh ideal configurational entropies:~2.7kB per cation or higher on one sublattice in most cases).Notably,(15RE_1/15)(Nb_1/2Ta_1/2)O₄ possess a single monoclinic fergusonite(C2/c)phase,and(15RE_1/15)₃(Nb_1/2Ta_1/2)₁O₇ form a single orthorhombic(C222₁)weberite phase,where 15RE_1/15 represents Sc_1/15Y_1/15La_1/15Pr_1/15Nd_1/15Sm_1/15Eu_1/15Gd_1/15Tb_1/15Dy_1/15Ho_1/15Er_1/15Tm_1/15 Yb_1/15Lu_1/15.Moreover,a series of eight(15RE_1/15)_2+x(Ti_1/4Zr_1/4Ce_1/4Hf_1/4)_2−2x(Nb_1/2Ta_1/2)_xO₇ specimens all exhibit single phases,where a pyrochlore–weberite transition occurs within 0.75相似文献   

Erratum to: Preparation of Mullite–TiC–ZrC-Ceramic Materials by a Plasma-ARC Method and Their Properties

Refractories and Industrial Ceramics -     

Erratum to: Preparation of Mullite–TiC–ZrC-Ceramic Materials by a Plasma-ARC Method and Their Properties

Refractories and Industrial Ceramics -     

Modifier–substrate interactions of various types in the Orito reaction: Reversal of the enantioselection in the hydrogenation of ketopantolactone on Pt modified by β-isocinchonine and O-phenylcinchonidine

The enantioselective hydrogenation of ketopantolactone (KPL) on Pt–alumina catalyst modified by β-isocinchonine (β-ICN) and O-phenylcinchonidine (PhOCD) in toluene, acetic acid and their mixtures under otherwise identical experimental conditions was studied. Reversal of the enantioselection was obtained dependent on the concentration of acetic acid (ee_max = 17% (S) on Pt–PhOCD and 50% (R) on Pt–β-ICN, respectively). The possible role in enantioselection of adducts forming in the reaction mixture and the stability of PhOCD under the conditions of the hydrogenation was investigated by ESI-MS. The results of the nonlinear phenomenon measurements on β-ICN + PhOCD mixtures suggest that the intermediate surface complexes β-ICN–KPL and PhOCD–KPL responsible for the opposite enantioselection include different types of interactions and the enantioselection is directed by the competition between these interactions.     

Preparation of nanostructure CuO/ZnO mixed oxide by sol–gel thermal decomposition of a CuCO3 and ZnCO3: TG,DTG, XRD,FESEM and DRS investigations

Nanostructure CuO/ZnO mixed oxide was systematically prepared via the sol–gel route using zinc and copper carbonates as precursors (molar ratio of 2:1) under thermal decomposition. The zinc and copper carbonates precursors have been synthesized by a simple chemical reaction in high yield and characterized by its melting point, FT-IR and thermal analysis (TG/DTG). The TG/DTG analysis proved that the thermal decomposition of zinc and copper carbonates precursors at 255 °C and 289 °C respectively. Thermo-gravimetric analysis (TG-DTG), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and diffuse reflectance spectroscopy (DRS) studies were undertaken to investigate the thermal properties and electronic structure of the CuO/ZnO mixed oxide catalysts. XRD data of the samples proved the formation of the nano-crystalline CuO/ZnO mixed oxide. Scanning electron microscopy (SEM) showed that the spherical-like particles have a diameter in the range 35–45 nm. Optical spectra of the nanostructure show a band peaked at 1.35 eV which is associated to near band gap transitions of CuO and a band centered at about 3.00 eV related to band gap transitions of ZnO nanostructures.     

Air–steam gasification of biomass in a fluidised bed: Process optimisation by enriched air

The effect of oxygen concentration in the gasification agent was studied by enriched–air–steam biomass gasification tests in a bubbling fluidised-bed gasification (FBG) plant. The oxygen content in the enriched air was varied from 21% (v/v, i.e. air) to 40% (v/v), aiming at simulating FBG where enriched air is produced by membranes. The stoichiometric ratio (ratio of actual to stoichiometric oxygen flow rates) and steam-to-biomass ratio (ratio of steam to biomass, dry and ash-free, flow rates) were varied from 0.24 to 0.38 and from 0 to 0.63, respectively. The tests were conducted under simulated adiabatic and autothermal conditions, to reproduce the behaviour of larger industrial FBG. The temperature of the inlet gasification mixture was fixed consistently at 400 °C for all tests, a value that can be achieved by energy recovery from the off-gas in large FBG without tar condensation. It was shown that the enrichment of air from 21 to 40% v/v made it possible to increase the gasification efficiency from 54% to 68% and the lower heating value of the gas from 5 to 9.3 MJ/Nm³, while reaching a maximum carbon conversion of 97%. The best conditions were found at intermediate values of steam-to-biomass ratio, specifically within the range 0.25–0.35. The enriched-air–steam gasification concept explored in this work seems to be an interesting option for the improvement of standalone direct air–blown FBG because it considerably improves the process efficiency while maintaining the costs relatively low as compared to oxygen-steam gasification.     

Catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-Mn-Cu/γ-Al2O3 in a rotating packed bed

This study investigated catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-Mn-Cu/γ-Al₂O₃ (Cat) in a rotating packed bed (RPB) for the first time. The results showed that the value of the overall decomposition rate constant of ozone (K_c) and overall volumetric mass transfer coefficient (K_La) are 4.28×10^-3 s^-1 and 11.60×10^-3 s^-1 respectively at an initial pH of 6, β of 40, of 60 mg·L^-1 and Q_L of 85 L·h^-1 in deionized water, respectively. Meanwhile, the K_c and K_La values of Fenhe water are 0.88×10^-3 s^-1 and 2.51×10^-3 s^-1 lower than deionized water, respectively. In addition, the K_c and K_La values in deionized water for the Cat/O₃-RPB system are 44.86% and 47.41% higher than that for the Cat/O₃-BR (bubbling reactor) system, respectively, indicating that the high gravity technology can facilitate the decomposition and mass transfer of ozone in heterogeneous catalytic ozonation and provide some insights into the industrial wastewater.     

Overcoming the quality–quantity tradeoff in dispersion and printing of carbon nanotubes by a repetitive dispersion–extraction process

Dispersion-printing processes are essential for the fabrication of various devices using carbon nanotubes (CNTs). Insufficient dispersion results in CNT aggregates, while excessive dispersion results in the shortening of individual CNTs. To overcome this tradeoff, we propose here a repetitive dispersion–extraction process for CNTs. Long-duration ultrasonication (for 100 min) produced an aqueous dispersion of CNTs with sodium dodecylbenzene sulfonate with a high yield of 64%, but with short CNT lengths (a few μm), and poor conductivity in the printed films (∼450 S cm⁻¹). Short-duration ultrasonication (for 3 min) yielded a CNT dispersion with a very small yield of 2.4%, but with long CNTs (up to 20–40 μm), and improved conductivity in the printed films (2200 S cm⁻¹). The remaining sediment was used for the next cycle after the addition of the surfactant solution. 90% of the CNT aggregates were converted into conductive CNT films within 13 cycles (i.e., within 39 min), demonstrating the improved conductivity and reduced energy/time requirements for ultrasonication. CNT lines with conductivities of 1400–2300 S cm⁻¹ without doping and sub-100 μm width, and uniform CNT films with 80% optical transmittance and 50 Ω/sq sheet resistance with nitric acid doping were obtained on polyethylene terephthalate films.     

SO2 Removal by Seawater in a Packed–Bed Tower: Experimental Study and Mathematical Modeling

Flue gas desulfurization of industrial plants using seawater is studied experimentally and theoretically in a counter–current packed–bed tower. Experiments are carried out based on a 16–run orthogonal array of the Taguchi method (five factors, four levels) and ANOVA table created to determine the most significant controlling factors on SO₂ removal efficiency. Liquid flow rate (1.5–4 l/min), gas temperature (50–350°C), gas flow rate (8–20 m³/h), and SO₂ concentration (500–2000 ppmv) are revealed as important factors, while the pH of seawater (8–9.5) is not significant. Experimental results show that an increase in gas temperature causes a decrease in the removal efficiency. A mathematical model is developed for the removal of SO₂ by seawater for non-isothermal operating conditions. In the modeling procedure the equilibrium reactions of eight dissolved species within the liquid phase are considered to calculate the kinetic of reaction correctly. The results of this study confirm the capability of seawater for SO₂ removal in packed-bed towers.     

Fiber-stretching test: a new technique for characterizing the fiber–matrix interface using direct observation of crack initiation and propagation

A new micromechanical technique for experimental determination of fiber-matrix interfacial properties is presented. This technique consists in tensile loading of the fiber, with a matrix droplet on it, at both ends, accompanied by continuous direct observation of interfacial crack propagation. In comparison with the well-known microbond test, the new method has two important advantages. First, crack propagation is stable for any embedded fiber length and any relation between adhesion and friction at the interface. Second, compliance of the test equipment does not affect the results, and specimens with long free fiber ends can be successfully tested. A similar result can be reached using the pull-out or microbond test with an 'infinite' (very long) embedded fiber length. An algorithm for separate determination of the interfacial adhesion and friction from experimental relationships between the crack length and applied load is described. The new test was employed to determine the interfacial parameters for composites of glass fibers with polypropylene, polystyrene, and polycarbonate. For each fiber-polymer system investigated, the following parameters were calculated: ultimate interfacial shear strength; critical energy release rate for crack propagation; and adhesional pressure. Our approach to the estimation of the work of adhesion, WA, from micromechanical tests, based on the concept of adhesional pressure, allowed us to calculate the WA values for several thermoplastic matrix-glass fiber pairs and to obtain values consistent with previous estimations made according to other approaches.     

Alkanol-Induced Micelles of a Very Hydrophilic EO–PO–EO Block Copolymer: Characterization by Spectral and Scattering Methods

The aqueous solution behavior of a PEO–PPO–PEO block copolymer (EO₁₀₃PO₃₉EO₁₀₃), was investigated in the presence of aliphatic alkanols (C₂, C₄, C₆ and C₈). The non-associated polymer chains remain extremely hydrated in water, but aggregation in the form of spherical micelles was evidenced, triggered by the interaction of polymer chains with hydrophobic alkanol. We assume that the hydrophobic interaction between the PPO block of the copolymer and alkanol promotes micellization, which increases further with the introduction of higher chain length species. The critical micellization temperature (CMT), as measured by UV–visible spectroscopy, indicates an interaction of polymer chains with the alkanol bearing a higher chain length, which triggers aggregation. The micelles were characterized by small angle neutron scattering to elucidate the size and related micellar parameters. The gradual increase in the alkanol content increases the aggregation number, though the micelles were spherical in shape. We conclude that ethanol, due to its preferential solubility in the aqueous phase, does not affect the aggregation. The alkanols with chain lengths of C₄–C₈ chain, interact with the PPO block through hydrophobic interaction and shifts the CMTs to lower values. The combined effect of inorganic salt (NaCl) and alkanols show enhanced micellar properties.     

Reaction of the titanocene alkyne complex Cp2Ti(η2-Me3SiC2SiMe3) with selenium dioxide: Preparation and characterization of a novel tetranuclear titanium complex with selenium and oxo bridges

The low valent titanocene(II) source Cp₂Ti(η²-Me₃SiC₂SiMe₃) 1 reacts with selenium dioxide (2) to obtain a tetranuclear selenium and oxygen bridged titanocene(IV) [{Cp₂Ti(µ²-O; µ²-Se)CpTi}₂(µ²-O)] 6. The molecular structure was confirmed by X-ray analysis.     

Synthesis and characterization of polyaniline–titanium(IV)phosphate cation exchange composite: Methanol sensor and isothermal stability in terms of DC electrical conductivity

Electrically conductive composite of polyaniline–titanium(IV)phosphate (PANI–TiP) was synthesized by sol–gel method. The obtained composite was characterized by using Fourier transform infra red spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The composite showed good ion-exchange capacity and isothermal stability in terms of DC electrical conductivity retention at an ambient conditions below 100 °C. The composite material was investigated as alcohol vapors sensor and compared with blank polyaniline. The results showed that the composite was more selective and sensitive towards methanol vapors.     

Kinetic and Thermodynamic Separation of Cu(II) and Fe(III) by Liquid-Liquid Extraction with a β-Hydroxy-oxime in Toluene

Abstract

A quantitative study of the thermodynamic and kinetic separation of Cu(II) and Fe(III) by liquid-liquid extraction with toluene solutions of the oxime 2-hydroxy-5-t-octyl (acetophenone oxime) has been conducted. On the basis of the stoichiometry, equilibrium constants, rate laws and rate constants of the extraction reactions of Cu(II) and Fe(III) an equation has been derived which describes how the separation of Cu from Fe varies with the chemical composition of the system, the hydrodynamics of the extracting apparatus and the contact time between the aqueous and the organic phases. Our results show that separations which are not feasible thermodynamically are possible when the contact time between the two phases is kept much shorter than that required to reach equilibrium.